Compositions for stabilizing chlorinated water to sunlight decomposition, and methods of preparation thereof

Abstract

The invention includes a composition for stabilizing chlorinated water to sunlight decomposition, and methods of preparing compositions. The composition is a slurry composition of a monoalkali metal cyanurate, of low viscosity. Two methods of preparing the slurry are described, in which cyanuric acid or cyanuric acid wetcake is mixed with a monoalkali metal base. One method dry blends cyanuric acid or cyanuric acid wetcake with a monoalkali metal base. The invention also describes a method of preparing a dry, solid monoalkali metal cyanurate.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to compositions, and the methods of preparing the compositions, for stabilizing chlorinated water to sunlight decomposition. In particular, the invention includes a monoalkali metal cyanurate slurry and methods for preparing the slurry and a dry solid.[0003]2. Description of the Related Art[0004]For disinfection and biocontrol, chlorine is introduced to many different bodies of water that are exposed to direct sunlight. Examples include outdoor swimming pools, cooling towers, ornamental fountains and wastewater lagoons. There are a variety of ways of chlorinating these waters: sparging with gaseous Cl2; using a chemical delivery pump for liquid sodium hypochlorite (NaOCl) solutions; via erosion feeder for solid, tableted chlorine-donating chemicals such as Ca(OCl)2 and trichlorotriazinetrione; by hand-broadcasting fast-dissolving solid chlorine donating chemicals such as sodium dichlorotriazinetri...

AI Technical Summary

Benefits of technology

[0014]The invention includes methods for producing a slurry and a dry solid of a monoalkali metal cyanurate that can be added to chlorinated water to stabilize the chlorine against UV degradation. The invention also includes a slurry composition of a monoalkali metal cyanurate. The slurry composition is low in viscosity, making it thin enough to be of practical value—it is pourable from any standard container and can be processed so that little is wasted by sticking to the equipment and reaction vessels. Moreover, the instant slurry composition resists settling or separation from the liquid phase, providing the end-user with a convenient and efficient product. Additionally, the slurry and dry solid compositions dispense and dissolve readily in water and are inexpensive and easily manufactured.

[0016]A second embodiment is another method for preparing a slurry of a monoalkali metal cyanurate in water. It was surprisingly found that cyanuric acid wetcake could be dry-blended with a solid monoalkali metal base at room temperature to yield a monoalkali metal cyanurate directly. This avoided the need for making a cyanuric acid slurry in water followed by reaction with a solution of a monoalkali metal base and the solid-liquid separation step. Thus, in this method, a cyanuric acid wetcake is mechanically blended with a solid monoalkali metal base to form a semi-dry solid cake. This solid is introduced to water under high speed mixing or homogenization. The water may optionally contain a suspension agent or dispersant. The slurry of a monoalkali metal cyanurate is produced after mixing for a prerequisite time.

Problems solved by technology

Unfortunately, the low solubility of cyanuric acid coupled with the low surface area of the granules means that the cyanuric acid may take several days to dissolve.

Lower water temperatures, which may occur when pools are filled for the first time, prolong this dissolution time even further.

The extended time that it takes for cyanuric acid to dissolve in pool water causes several problems.

First, the localized high acid condition in the vicinity of the undissolved cyanuric acid can etch or discolor the plaster of newly constructed gunite pools and can cause wrinkling and discoloration of the vinyl of vinyl-lined pools.

Second, the pool remains unstabilized to UV decomposition until all the cyanuric acid has dissolved, and biological control is difficult due to the rapid UV degradation of the disinfectant.

Third, the aesthetic appearance of the pool is compromised for several days due to piles of undissolved cyanuric acid lying at the bottom of the pool or ornamental water feature.

Fourth, the pool owner is unable to operate the pool vacuum during this time because the cyanuric acid would be sucked from the floor of the pool into the filter.

The resultant localized low pH condition in the filter and associated equipment would damage or impair the filtration systems and piping.

In the first place, monosodium cyanurate is not commercially available, probably due to a high cost of production.

The solid was said to be useful as an active chlorine stabilizer in pool water; however, the method is inefficient in producing large volumes and is still very costly.

Although the use of a slurry of monosodium cyanurate would appear to solve the problem of the high cost of production of solid monosodium cyanurate, it results in other problems.

It was found, however, that both the freshly-prepared and water-decanted slurries were so thick and viscous that they were of no practical value.

In the first place, the slurry was so thick and viscous that it could not be easily pumped out of a reaction vessel into a container.

Second, even if the slurry could be put into a container, the end-user would not be able to pour it out of its container into the pool; the user would have to scrape the slurry out with a separate tool or device.

Moreover, because the slurries are so heavy and massive, they would immediately sink to the bottom of the pool and remain in an undissolved clump.

This mass could not be removed from the container.